1. Field of the Invention
This invention relates to systems, methods, and apparatus for storing and presenting sample materials for access by a sample transfer apparatus and for limiting the incidence of cross-contamination between sample-containing vessels during a sample transfer operation.
2. Background of the Invention
All documents referred to herein, or the indicated portions, are hereby incorporated by reference herein. No document, however, is admitted to be prior art to the claimed subject matter.
Analyzers for performing assays on fluid samples typically include a fluid transfer mechanism for transferring fluid sample material and other fluids between various receptacles or containers. For example, fluid sample material may be introduced into the analyzer via a sample receptacle, such as a test tube, containing an amount of the fluid sample, placed in the analyzer or in operative proximity to the analyzer. The analyzer may include an automated fluid transfer mechanism comprising a robotically-controlled pipetting device having an aspirating probe for accessing the contents of a receptacle. The probe may comprises a barrel with a protective tip (e.g., a pipette tip) mounted (e.g., frictionally) on its distal end.
Fluid sample material is transferred from the sample receptacle by positioning the aspirating probe above the sample receptacle and then lowering the probe until a distal end of the probe is submerged in the fluid sample material held in the container. After the probe is submerged, an amount of fluid is drawn into the probe. The probe is then raised and moved to another location within the analyzer and is operatively positioned above another container (or, alternatively, the probe can be held in a fixed position and the sample receptacle and other containers can be moved relative to the probe). The sample material may be transferred to a reaction receptacle (e.g., test tube, cuvette, microtiter plate well, etc.) within which the sample material is combined with reagents and/or other reactants (and, optionally, the container and its contents may be subjected to other conditions or stimuli, such as, incubation at an elevated temperature, mixing, and/or centrifuging) to effect a transformation or chemical, biochemical or biological reaction. After the probe is positioned above the container that is to receive the sample material, some or all of the fluid is dispensed from the probe into one or more containers, moving the probe from receiving container to receiving container as necessary.
During such a fluid transfer procedure, care must be taken to avoid cross-contamination due to spilled or misplaced sample material. For example, sample from one sample receptacle should not be mistakenly deposited into another sample receptacle containing a different sample or a sample from a different source. Similarly, no sample material should be deposited into a reaction receptacle in which such sample is not intended, for example in a reaction receptacle within which a different sample had already been dispensed.
Fluid sample material may include, for example, urine, blood, plasma, saliva, mucus, seminal fluid, amniotic fluid, cerebrospinal fluid, synovial fluid, and cultures. Such materials may, under certain circumstances or conditions, be characterized as having a viscous consistency. Accordingly, when the probe of a pipetting device is submerged into the sample material and is then withdrawn, the viscous or mucoid nature of the sample material may result in a string of viscous material suspended from a distal end of the probe after the probe is withdrawn from the sample receptacle. Further movement of the sample transfer probe may drag the string of viscous material along with it, thereby potentially causing cross-contamination should the string of viscous material contact or fall into another sample receptacle or reaction vessel or other contamination-sensitive surface or component within the analyzer.